DVD-R not recognised by DVD Recorder.

I bought some blank DVD-Rs recently and they have proven to be very good quality for burning my own home videos onto as well as backing up my own pre-recorded movies on DVD. However, I want to record from my Sky+ box (satellite TV in UK) onto one of these discs. However, my DVD Recorder does not recognise it and a "No Disc" message appears when I load it into the tray. The DVD Recorder itself (a Phillips DVDR 880) can play these discs when they have been recorded onto by my DVD Burner on my PC. Also, it has recognised other blank DVD-Rs in the past and recorded onto them without any problem. The brand of DVD-R is Ritek (I think, it says RiDisc on the front).